Julia Roberts is grieving following the loss of her half sister (Picture: Getty)

A ‘devastated’ Julia Roberts pulled out of a pre-Oscars lunch after her half-sister was found dead following a suspected drug overdose.

The grieving star missed the do in Beverly Hills after 37-year-old Nancy Motes was found in her bathtub just after 2pm on Sunday by her fiancé John Dilbeck – with her sibling’s death shining a light on an apparent bitter and deep family feud.

‘It is with deep sadness that the family of Nancy Motes … confirms that she was found dead in Los Angeles yesterday of an apparent drug overdose,’ a statement for the 46-year-old actress’s family read.

‘There is no official report from the coroner’s office yet. The family is both shocked and devastated.’

Motes, described as a dog walker and pet sitter, shares the same mother, Betty Lou, as Roberts but have different fathers.

She and Roberts, who is up for best supporting actress next month for her role in August: Osage County, are thought to have shared a strained relationship with Motes growing up in the star’s shadow.

The aspiring actress and former Glee production assistant was 13 when her sister became a household name after starring in 1990 flick Pretty Woman.

‘I think that growing up as Pretty Woman’s little sister has definitely made me try to see the person inside and not the person outside,’ said Motes.

‘A lot of my life I felt judged for my weight.’

In an interview last summer, Motes then accused Roberts of taunting her in school over her size.

‘When I was in high school and she was an adult, she would just let me know that I was definitely overweight,’ Motes revealed.

‘It just makes me feel incredibly hurt and very sad.’

Motes finally underwent a gastric bypass surgery four years ago after ballooning to 300lbs (136kg).

Her relationship with the star appeared to have dissolved just three weeks before her death when she hit out on Twitter last month ranting: ‘So my ‘sister’ said that with all her friends & fans she doesn’t need anymore love. Just so you all know ‘America’s Sweetheart” is a B***H!!’

She added: ‘Do you want to be a fan of someone so cruel? She’s not even that good of an actress. Happy you totally F***ed with me?

‘I must admit I maybe going to far… But I never been so angry in my life. I’m actually a pretty easygoing, peaceful person.’

Motes’s body is now undergoing an autopsy with the toxicology results expected to take six to eight weeks to get back.